This invention relates in general to fittings for connecting structures together and, more specifically, to a self-tightening fitting for connecting metal and carbon-carbon structures.
High temperature and high vibration levels are encountered in many aerospace applications, both in spacecraft and in hypersonic aircraft. A variety of different structural materials are required for this structure to provide high strength, resistance to very high temperatures together with light weight. Various metal alloys and composite materials are being considered for use in such applications.
Carbon-carbon composites are being considered as a structural material designed to operate in a hot sonic environment. Examples of these structures included afterburning vectoring nozzles for future military aircraft and hot structures found on transatmospheric hypersonic aircraft. In these applications, the carbon-carbon materials will encounter sound pressure levels as high as 180 dB and temperatures well over 1000.degree. C.
The carbon-carbon materials must be securely fastened to underlying vehicle structure, which is generally formed from metals having coefficients of thermal expansion (CTE) much higher than carbon-carbon. Many fittings fail when subjected to the vibration levels and thermal cycling encountered in these applications. Also, since the carbon-carbon materials are subject to wear or erosion in many of these applications, vehicle designers must provide for quick and convenient removal and replacement of the carbon-carbon structure at the fittings.
Thus there is a continuing need for metal to carbon-carbon structure fittings capable of remaining tight under these severe conditions while permitting easy removal when necessary.